Scale inhibitors are used in production wells to prevent scaling in the formation and/or in the production lines downhole and at the surface. Scale build-up decreases permeability of the formation, reduces well productivity and shortens the lifetime of production equipment. In order to clean scales from wells and equipment it is necessary to stop the production which is both time-consuming and costly.
Several methods are known in the art for introducing scale inhibitors into production wells. For instance, a liquid inhibitor may be forced into the formation by application of hydraulic pressure from the surface which forces the inhibitor into the targeted zone. In most cases, such treatments are performed at downhole injection pressures below that of the formation fracture pressure. Alternatively, the delivery method may consist of placing a solid inhibitor into the producing formation in conjunction with a hydraulic fracturing operation. This method is often preferred because it places the inhibitor in contact with the fluids contained in the formation before such fluids enter the wellbore where scaling is commonly encountered.
A principal disadvantage of such prior art methods is the difficulty in releasing the inhibitor into the well over a sustained period of time. As a result, treatments must repeatedly be undertaken to ensure that the requisite level of inhibitor is continuously present in the well. Such treatments result in lost production revenue due to down time.
Treatment methods are therefore sought for introducing scale inhibitors into oil and/or gas wells wherein the inhibitor may be released over a sustained period of time. It is desired that such methods not require continuous attention of operators over prolonged periods.